DNA probes developed by Gen-Probe, Inc. (San Diego, CA) have been demonstrated to be useful for the rapid identification of certain species of mycobacteria directly from colonies grown on solid media. Many clinical specimens for mycobacterial culture are planted in liquid media and are first positive in that media. Thus it would be useful to be able to use the probes on mycobacteria grown in liquid media. Various techniques for processing liquid media have been evaluated to assess their usefulness in combination with probe technology for mycobacterial identification. This study has demonstrated that the probes can be used directly on concentrates from liquid media. For blood cultures done in BACTEC 13A media (Johnston Laboratories, Towson, MD), the probes for Mycobacterium avium - intracellular can be done once a growth index of >= 86 has been attained.